The present invention is directed, in general, to semiconductor wafer cleaning brushes and, more specifically, to a semiconductor wafer cleaning brush assembly having a contractible and expandable arbor.
During semiconductor manufacturing, several processes create debris that must be removed from the semiconductor wafers to prevent any contamination of the integrated circuits (ICs) derived from the wafers. Some of the processes well known for depositing contaminating particles on the surface of semiconductor wafers are silicon polishing, laser scribing and chemical/mechanical polishing.
Silicon polishing is performed after a silicon ingot is cut into wafers to prepare the wafers for further precessing. Laser scribing is the process by which identifying numbers are scribed into the wafer, and chemical/mechanical polishing uses an abrasive slurry to planarize the wafer surface. Each of these processes creates debris or chemical residue that may adhere to the wafer surface and present a potential contamination hazard. However, the most common particles left on the wafer are metals from a metal CMP process and dielectric oxide materials from a dielectric CMP process. Among these particles are tungsten, titanium, titanium nitride, aluminum, tantalum, copper, polishing pad particles and slurry particles. With the high cost of semiconductor manufacturing and intense competition among manufacturers, every effort must be made to minimize the contamination hazard presented by one of more of these particles. Additionally, even fewer defects per area of semiconductor material are required for smaller geometries for the devices to be considered functional.
Thus, for reasons of both thoroughness and efficiency, these contaminants are perhaps best removed from the wafer surface by a combination of chemical and mechanical means. In a typical wafer cleaning apparatus, the surfaces of the semiconductor wafer are best cleaned of any residual debris by passing the wafer between two rollers equipped with cleaning brushes usually constructed of polyvinyl alcohol (PVA). Ammonium hydroxide or dilute hydrofluoric acid is also commonly used as a component of the cleaning solutions used for semiconductor wafer cleaning. In addition, the PVA cleaning brushes may also be kept wetted with de-ionized water to provide the high quality surface necessary for removing debris. While in use, the combination of brush rotation and pressure applied to the semiconductor wafer through the brushes provides for the proper cleaning of the semiconductor wafer surfaces.
Once a cleaning brush has exceeded its useful life and can no longer adequately clean the wafer surface, the brush must be replaced. In spite of the advances achieved in successfully removing the contaminants from wafer surfaces, replacement of such cleaning brushes still presents a problem. The brushes must be held snugly by the roller on which they are mounted to prevent bunching-up of the brush surface during the cleaning process. If any portion of the brush surface is permitted to bunch-up or wrinkle during cleaning, an uneven brush surface is created and the irregular raised portions of the brush may inadvertently scratch or other wise damage the wafer. In addition, the portions of the brush surface that remain wrinkle-free may now be unable to contact the wafer surface to effectively clean the wafer surface.
To prevent the cleaning brushes from developing any wrinkles or otherwise bunching-up during the cleaning process, the brushes must be held very securely by their respective rollers, and thus have been forcibly stretched and pulled around the roller. Although the material of the cleaning brush is often somewhat pliable, those skilled in the art still find the task of removing and replacing a cleaning roller in such a manner a tedious and labor-intensive affair. Additionally, these difficulties may even increase depending on the person attempting to replace the cleaning brush.
Numerous problems abound when a cleaning brush is forcibly stretched around a mounting roller. Perhaps most notably, by forcing a cleaning brush onto a larger roller, the brush material may tear or become otherwise damaged. Understandably, when the brush is so damaged it may no longer retain its original strength and prematurely wear during the cleaning process. Due to the expense of replacing wafer cleaning brushes, it is desirable to extend the life of the cleaning brushes as long as possible. Moreover, should the brush material completely fail during the cleaning process, the exposed roller surface may severely damage the wafer being cleaned, an expensive gamble in today""s competitive semiconductor market.
In addition to the risk of damaging the brush itself, forcibly applying a brush to a roller is a time-consuming task. Beyond the frustration that can develop when a technician is required to forcibly stretch a cleaning brush over a roller, the time necessary to successfully change the brush results in lost down-time for the cleaning apparatus. While the technician struggles with removing and replacing the brush, the cleaning apparatus is unable to clean incoming semiconductor wafers. Thus, the manufacturer incurs revenue loss due to the excess time the cleaning apparatus is out of commission. Moreover, even though great care may be taken while stretching the brush over the roller, forcibly stretching material in such a manner may still result in wrinkles on the brush surface.
Prior art efforts to minimize the damage likely caused by forcibly stretching the brushes onto their rollers are scarce at best. One such effort involves a device coated with a low friction material, such as Teflon(copyright), to assist in sliding the brush onto the roller. The low friction material creates a smoother interface between the inside of the brush and the outside of the roller while the brush is being mounted on the roller. Unfortunately, even this effort to xe2x80x9cshoe-hornxe2x80x9d the brush onto the roller results in little relief from the problems discussed above. Whether a smoother interface is created, this prior art device still involves forcibly stretching the brush onto the roller, and as such, may still result in wrinkling, tearing or over-stretching the brush material. Over time, this device is repeatedly scraped and scratched during the mounting process, which may result in scraped particles removed from the device being deposited on the wafer surface. Since the cleaning process is designed to rid wafers of contaminating particles, a device that inadvertently deposits contaminants on the wafer surface may be more detrimental to the cleaning process than helpful.
Accordingly, what is needed in the art is a way of mounting a cleaning brush to the roller of a cleaning apparatus that does not suffer from the deficiencies found in the prior art.
To address the above-discussed deficiencies of the prior art, the present invention provides a semiconductor wafer cleaning brush assembly having an arbor with an expandable member configured to have a non-expanded position and an expanded position, and a cleaning brush, loadable about the expandable member, having an inner diameter greater than an outer diameter of the expandable member in the non-expanded position and less than an outer diameter of the expandable member in the expanded position. One or more such brush assemblies may be placed within a cleaning apparatus for cleaning the surfaces of a semiconductor wafer.